The Tissue Accrual and In Situ Imaging Core is responsible for accrual of human melanomas, nevi and blood sample, for in situ imaging of melanoma- associated antigens and RNA species in sections of human melanomas and nevi, and for the provision of expert pathological interpretation of histological data. Refined immunohistochemical methods have been developed that enable the identification of antigens in archival tissue without requiring expensive and C special handling including frozen specimens or special fixatives. In situ hybridization procedures using biotinylated oligonucleotide probes are used to identify mRNA for important melanoma- associated antigens. Antibodies and/or probes that are available in fixed tissue include the immune co-stimulatory molecule B7 (project of D. Guerry), TGFbeta1-3 (U. Rodeck), an MUC18 (M. Herlyn). The fresh tissue accrued by the Core has already resulted in one of the largest collections of primary melanocytic cell cultures (M. Herlyn), and in a very large collection of freshly isolated DNA used for genetic studies (A, Linnenback). The Core has extensive access to human tissue biopsies including thousands of pigmented lesions in the affiliated laboratories of Surgical Pathology (20,000 accessions/year) and of dermatopathology (40,000). This tissue is available for the evaluation of new antibodies produced in the projects of D. Speicher and D. Herlyn, and for the molecular in situ studies planned in Dr. Linnenbach's project. Expertise in all aspects of the pathological diagnosis and classification of melanocytic neoplasms is provided to the projects on a continuing basis.